To characterize the deletion patterns and its breakpoints in oligozoospermic patients presenting AZFb and AZFc microdeletions and to understand the recombination mechanisms underlying these microdeletions.Case report.Genetics Department of Faculty of Medicine of Porto, Porto, Portugal.Two men with severe oligozoospermia and two men with nonobstructive azoospermia identified as having different AZFb+c deletion patterns via Y chromosome microdeletion analysis.Definition of microdeletions and the fine characterization of the respective breakpoints by sequence-tagged sites (STS) polymerase chain reaction (PCR) and single-nucleotide variant (SNV) PCR.Study of the fine structure of the Y-chromosome and discussion of the putative mechanisms involved in each microdeletion pattern.From the four patients studied, three deletion patterns were identified: IR4/distal-P2 (25%; 1 of 4), P5/proximal-P1 (50%; 2 of 4), and P5/distal-P1 (25%; 1 of 4). Although severe oligozoospermia is normally associated with AZFc, a complete AZFb deletion was found in one case.Analysis of these patients has revealed a new putative region that may be involved in spermatogenesis conservation.